Adherent orthotic pad

ABSTRACT

An orthotic pad is disclosed for reducing pressure and shear stresses on dermal and muscle tissue in treatment areas extending over bony prominences. This pad includes a hydrocolloid-containing adhesive body having oppositely-facing non-parallel first, and second major surfaces. The pad is formed of a soft, deformable and shape-recoverable adhesive material in which particles of at least one moisture-absorbing and moisture-swellable hydrocolloid material are dispersed. The first surface of the pad is contoured to match that of the treatment area for adhesively engaging and covering such area, and the second surface has a developed shape for corrective redistribution of external forces exertable against the treatment area to prevent further damage from pressure or shear forces, promote the healing process and, in appropriate cases, provide orthopedic correction.

BACKGROUND AND SUMMARY OF THE INVENTION

[0001] Pressure ulcers are areas of skin death caused by excessivepressure or shear, either one of which will close off the flow of bloodin the skin vessels. In general, the risk of tissue death is increasedwith higher levels of pressure or shear stress, and with longer durationof the pressure or shear insult.

[0002] Bony prominences are concentrators of pressure, and so skin overthese areas on the body is especially at risk to pressure injury. Suchareas where bone is not padded much by muscle also can be areas wherehigh shear stresses in the skin are encountered, as a person sits, lies,or stands on a surface.

[0003] In healthy individuals, the body is constantly repositioned so asto relieve areas of excessive pressure and shear. Even in sleep, anindividual senses the need to reposition the body to relieve pressureand shear, and does so many times throughout the night.

[0004] Certain individuals are impaired in their ability to either sensethe need to reposition, or in their ability to do so. For example, anindividual who is recovering from hip surgery may feel the need to moveto another position as he/she lies bed, but may be unable to do so.Other individuals may be so critically ill that they are not aware ofthe need to reposition their bodies to relieve areas of the skincirculation that are compromised by pressure or shear stresses. Suchpatients are especially prone to developing ulcers in the sacrum,coccyx, and heel areas.

[0005] An extreme case is the individual that has no sensation in theskin at all, such as a paraplegic. These people cannot feel the skinthat is in contact with a chair's surface, and so are very likely todevelop pressure ulcers on the skin where they sit every day. Theysimply have no way of knowing when it is necessary to repositionthemselves, or to know when the repositioning was effective. Suchpatients often develop pressure ulcers over the ischium.

[0006] Diabetic individuals have this same problem with their feet.Their disease results in peripheral neuropathy, where the nerves of thefeet no longer function. Since their sensory nerves are not functioning,they cannot know when pressure or shear has become excessive in theirfeet. An object in the shoe that is causing a pressure ulcer isunnoticed. Excessive pressure over a metatarsal bone is unnoticed. Sheardue to a certain pattern of walking, or due to an unfavorable shoe fit,is unnoticed.

[0007] The motor neurons in the feet of diabetics are also affected bythe disease, and this can lead to muscle deformities. These muscleproblems will alter the structure of the foot, so the foot is positionedin an abnormal way during walking. This leads to areas of the skin thatsee abnormally high pressure and shear as the person walks. The muscleabnormalities can also lead to an altered gait, or way of walking, sothat both feet are affected by an abnormality developed in one foot.

[0008] To deal with these problems, diabetics are often given customorthotics in the form of relatively rigid shoe inserts that are made tomatch the surface of the bottom of the foot on one side. The other sideof the orthotic is designed to contact the shoe surface in such a way asto help correct for the foot deformity and resulting gait abnormality.Using the orthotic in the shoe helps to normalize the way pressure andshear are distributed on the foot during walking. However, such customorthotics are neither adhesive nor absorbent. As a result, the orthoticsmay easily become misaligned with the bottom of the foot to which theyare custom designed to fit, thereby potentially compounding the problem.

[0009] Diabetics seem to be especially sensitive to shear damage. Theirblood vessels are more fragile than those of normal individuals, soshear stress can cause bruising more easily in diabetics. This is aproblem in the foot, because shear is a normal part of the walkingprocess.

[0010] Once a pressure ulcer has developed, treatment will fail unlessthe pressure and shear issues are resolved. For example, in diabetics,if an ulcer is present on the plantar surface of the foot, this ulcerwill not heal unless measures are taken to ensure that toe ulcer area isprotected from pressure and shear damage during walking. Even very briefepisodes of excessive pressure or shear can damage the very fragiletissue, and set the healing process back. It is not practical to ask apatient to refrain completely from walking for the months required toheal an ulcer. Orthotics can help, but even an evening trip to thebathroom in bare feet can cause significant damage to the wound site.

[0011] One strategy that has been tried with success in these situationsis the total contact cast. A doctor encloses the foot in a plaster castdesigned so that walking will not result in further damage to the woundarea. This is, in a sense, an orthotic that is always in place, and infact cannot be removed except by the doctor. There are somedisadvantages to the total contact cast, however. One cannot reach thewound for dressing changes. One cannot inspect the wound, and the skinaround the wound, for developing problems. The cast itself can causepressure points if it is not optimally applied, and again this cannot bedetected without removing and then reapplying the cast. Applying thecast is a time consuming process that requires some skill.

[0012] An important aspect of this invention therefore lies in providingan orthotic device that is particularly effective in eliminating orreducing pressure and shear stresses on dermal and muscle tissues intreatment areas extending over bony prominences. The device takes theform of an adhesive absorbent pad with a body-contacting surfacecontoured to conform with the skin surface in the area of treatment andwith an opposite surface of a different shape determined by the surfacesor objects to be engaged and the deformities if any to be corrected.Specifically, the pad includes an adhesive body or layer of a soft,deformable and shape-recoverable, pressure-sensitive adhesive materialin which particles of at least one moisture-absorbing andmoisture-swellable hydrocolloid material are dispersed. Theoppositely-facing major surfaces of the pad are non-parallel, with anadhesive body-facing first surface being contoured to match the shape ofthe treatment area and the oppositely-facing second surface having adeveloped shape for corrective redistribution of external forcesdirected against the area of treatment. The second surface of theadhesive body is covered by a tough, durable protective layer which maybe either flexible or rigid and may, if desired, be extended to coverthe side edge surfaces of the adhesive body as well.

[0013] Other features, objects and advantages of the invention willbecome apparent from the specification and drawings.

DRAWING

[0014]FIG. 1 is a longitudinal sectional view of an adhesive footorthotic embodying this invention.

[0015]FIG. 2 is a vertical sectional view taken along line 2-2 of FIG.1.

[0016]FIG. 3 is a sectional view taken along line 3-3 of FIG. 1.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

[0017] Referring to the drawings, FIGS. 1-3 depict an adherent orthoticpad 10 for treatment of a foot 11, and particularly for protectivetreatment of a wound 12, such as a pressure ulcer, along the plantarsurface of the foot extending over a bony prominence at the metatarsaljoint. While a foot orthosis is illustrated, it is to be understood thatthe invention is not limited to an orthotic pad for treatment of thefoot. The drawings show only one embodiment of the invention, but otherembodiments may include adherent orthotic pads for treatment areas wheredermal and muscle tissue have developed pressure ulcers such as, forexample, the sacrum, coccyx, elbow, or any other part of the bodyexposed to pressure or shear insult resulting from the concentration andextended duration of external pressures producing circulatoryinsufficiencies and tissue death.

[0018] The pad comprises a hydrocolloid-containing adhesive body 13 anda protective outer covering 14. The body is formed entirely of a soft,deformable, pressure-sensitive, hydrocolloid-containing adhesivecomposition, commonly referred to as a skin barrier composition, that isgenerally non-flowable, retains its integrity upon hydration, and hasshape-recovering properties. It must be capable of adhering to the skinfor extended periods, but the adherence must not be so aggressive as torisk skin injury or irritation during use and at the time of removal. Itshould also have sufficiently high cohesive strength to resistdisintegration throughout its duration of use and to remain intact atthe time of removal so that little or no residue remains adhered to theskin.

[0019] Such adhesive skin barrier compositions are known for use inostomy and wound care and typically comprise a discontinuous phasecomposed of particles of one or more hydrocolloids dispersed throughouta continuous water-insoluble elastomeric adhesive phase. Initial tack,usually referred to as dry tack, is provided by the continuous phasebut, because such a barrier material is occlusive or non-breathable,adherence to the skin would be disrupted by perspiration if it were notfor the dispersed hydrocolloids which absorb fluids and thereby maintainand possibly enhance adhesive attachment to the skin. U.S. Pat. Nos.5,492,943 and 4,551,490 disclose suitable water-absorbing and swellablehydrocolloid gums including sodium carboxymethylcellulose, pectin,gelatin, guar gum, locust bean gum, gum karaya, and mixtures thereof.The elastomers used in the continuous phase commonly includepolyisobutylenes, which may be either of relatively low viscosityaverage molecular weight (about 36,000 to about 58,000) or of highermolecular weight (for example 750,000 to 2,350,000). The elastomer phasemay also contain a styrene block co-polymer component to help provideextensibility and recovery from modular strains. While proportions mayvary, such skin barrier compositions generally have a hydrocolloidcontent within the range of about 35% to 70% by weight of the totalcomposition and an elastomeric adhesive phase in the range of about 20%to 40% of that total. In addition, such a composition may includehydrocarbon plasticizers consisting of petrolatum or mineral oil, andsuitable tackifying and antioxidant agents. For more detailedinformation concerning such skin barrier compositions, reference may behad to the abovementioned patents, the disclosures of which areincorporated by reference herein.

[0020] A characteristic aspect of an orthotic pad embodying thisinvention lies in the fact that the two major surfaces of the adhesivebody 13 are of different shape or contour and are non-parallel,resulting in a body of differing thickness or depth throughout itsoutline area. A first or body-facing surface 13 a is shaped to match thecontour of the body part to which the adhesive orthotic pad is to beadhered, whereas the second or outwardly facing surface 13 b is of adifferent shape designed for corrective redistribution of externalforces exertable against the body part. If the adherent pad takes theform of a foot orthotic as shown, then the second surface 13 b may besubstantially planar, matching that of a floor or other planar supportsurface upon which the patient's foot may be placed. However, in thecase of a patient having foot deformities that tend to produceabnormally high pressure and shear areas when the patient stands andwalks, the outwardly facing surface 13 b of the pad may be of developedshaped to help correct defects in the patient's gait. By redistributingexternal forces applied to the foot so that localized areas of excessivepressure or shear over bony prominences are avoided, the formation ofpressure ulcers in such areas may be prevented and the healing of ulcersin such areas may be promoted.

[0021] Protective layer 14, also referred to herein as a protectivelayer 14, or simply a covering 14, covers the outer surface 13 b of theadhesive layer and matches the shape or contour of that surface. In apreferred embodiment, the protective layer or cover also extendsupwardly about the side edges or surfaces 13 c of the adhesive layer asshown in the drawings. Covering 14 may be formed of any tough anddurable material capable of withstanding contact with external objectsand surfaces, and the covering can be flexible or rigid. A toughflexible polymeric film, such as one formed of a polyolefin, is believedsuitable, but other materials, such as fabrics of natural and syntheticfibers, may be used. The protective covering layer 14 is of generallyuniform thickness throughout its full extent, but its outwardly-facingsurface may be patterned or textured to prevent slipping and providetraction upon engagement with a support surface. Preferably, theprotective layer 14 is rigid and textured for foot orthotics, and rigidand smooth for orthotic pads intended for use elsewhere on the body.

[0022] Any of a number of methods may be used to form the foot orthotic10 so that its body-facing surface 13 matches the contour of the fulltreatment area which the orthotic is to adhesively engage—in this case,the entire underside of a patient's foot. Such methods include making aplaster cast of the foot, using that cast to make a positive mold, andthen molding the body of skin barrier material about one side of thepositive mold. Other methods include using a laser scanner combined with3D CAD software to develop a positive mold that duplicates the treatmentsurface to be protected and then using that mold to produce an orthoticin which a surface of the adhesive body matches the surface to which theorthotic is to be adhered. While the term “matching” is used to describethe contour of the body-facing surface of the adhesive pad or device,ordinarily where the body surface to be treated has a wound with asubstantial depression or cavity 12, the surface of the adhesive pad isformed to span that depression or cavity (as shown in FIGS. 1 and 2)rather than project into the wound.

[0023] While in the foregoing, an embodiment of the invention has beendisclosed in detail for purposes of illustration, it will be understoodby those skilled in the art that many of these details may be variedwithout departing from the spirit and scope of the invention.

1. An orthotic pad for reducing pressure and shear stresses on dermaland muscle tissue in a selected treatment area extending over a bonyprominence, comprising a hydrocolloid-containing adhesive body havingoppositely-facing non-parallel first and second major surfaces andcomprising a soft, deformable and shape-recoverable adhesive material inwhich particles of at least one moisture-absorbing andmoisture-swellable hydrocolloid material are dispersed; said firstsurface being contoured to match the contour of said treatment area foradhesively engaging and covering said area; said second surface having aselected shape different than said contour of said first surface; and aprotective layer covering said second surface.
 2. The orthotic pad ofclaim 1 in which said protective layer is of substantially uniformthickness and conforms with said surface shape of said second surface.3. The orthotic pad of claims 1 or 2 in which said protective layer isflexible.
 4. The orthotic pad of claims 1 or 2 in which said protectivelayer is rigid.
 5. The orthotic pad of claims 1 or 2 in which saidsecond surface is generally planar.
 6. The orthotic pad of claims 1 or 2in which said second surface is non-planar and of a developed shape forcorrective redistribution of external forces exertable against saidtreatment area.
 7. A foot orthotic for reducing pressure and shearstresses on dermal and muscle tissue in and about a wound area oftreatment, comprising a hydrocolloid-containing adhesive body havingoppositely facing non-parallel first and second major surfaces andcomprising a soft, deformable and shape-recoverable adhesive material inwhich particles of at least one moisture-absorbing andmoisture-swellable hydrocolloid material are dispersed; said firstsurface being contoured to match the contour of said treatment area foradhesively engaging covering said area; said second surface having aselected shape different than said contour of said first surface; and aprotective layer covering said second surface.
 8. The foot orthotic ofclaim 7 in which said protective layer is of said substantially uniformthickness and conforms with said surface shape of said second surface.9. The foot orthotic of claims 7 or 8 in which said second surface isgenerally planar.
 10. The foot orthotic of claims 7 or 8 in which saidsecond surface is non-planar and of a developed shape for correctiveredistribution of external forces exertable against said treatment area.